House dust mite-responsive human T cells require both interleukin 2 (IL2) and interleukin 4 for optimal proliferation, whereas IL2 alone is sufficient for proliferation of tetanus toxoid-responsive T cells.

Production of interleukin 4 (IL4) and response to IL4 may be a key determinant of the atopic immune response. Proliferation requirements of allergen-specific T cells derived from atopics and nonatopics were determined. Peripheral blood lymphocytes were cultured with either house dust mite (HDM) or tetanus toxoid under limiting dilution conditions with interleukin 2 (IL2) alone or IL2+IL4. The relative proportion of antigen-specific T cells responding under each of these conditions was determined by proliferation. The combination of IL2+IL4 resulted in the highest proportion of responding HDM-specific T cells. Similar results were obtained with HDM-specific T cells from both atopic and nonatopic donors. These HDM and Der pI responsive cells were found to be CD4+CD8-. In contrast, tetanus toxoid-responsive T cells from both atopic and nonatopic donors grew preferentially in response to IL2 alone.